3 Working with ASTs in code

In the previous chapter, you learned what an abstract syntax tree (AST) is and how to represent one using an object-relation diagram (ORD). In this chapter, you’ll learn how to put this representation into code, as in-memory data, and how to work with that encoded AST: inspect it, alter it, and traverse it. These skills will form the basis of the Domain IDE’s codebase. You’ll probably also encounter these notions outside of this book.

3.1 Turning ASTs into code

In this section, you’ll learn how to turn ASTs, which are notated in the ORD style we introduced in chapter 2, into data that a computer can work with. As announced in chapter 1, we’re going to implement our Domain IDE in JavaScript, so we’ll turn the AST into a JavaScript value. This process is called encoding: the AST is turned into JavaScript code that produces a JavaScript value that faithfully represents the AST.

3.1.1 Encoding containment relations

3.1.2 Encoding reference relations

3.2 Interacting with ASTs

3.2.1 Accessing concept labels and settings’ values

3.2.2 Recognizing AST and reference objects

3.3 Traversing ASTs

3.3.1 The general recipe for DFTT

3.3.2 Example: Counting the leaves of an AST

3.3.3 More about ASTs

Summary